The invention relates to a device for making notch cuts in continuous strip wrapping material.
Whilst the notching device disclosed is suitable for making transverse cuts in continuous strip wrapping material generally, its usefulness is realized to best advantage in the art field that embraces the packaging of commodities, and in particular, packs of cigarettes, for the purpose of making transverse cuts of substantially U-shaped appearance, spaced apart at regular intervals along tear-off ribbons of the type incorporated axially into continuous strips of transparent outer wrapping material, which enable easy removal of the wrapper subsequently formed from the transparent material simply by tearing it open.
The prior art in cigarette packaging machinery, cellophane wrapping machines in particular, embraces the use of notching devices comprising a revolving incision roller, mounted rotatably to a shaft and fitted with at least one blade that projects outward substantially in a radial direction from the surface of the roller and exhibits a substantially U-shaped profile when viewed in plan.
In most conventional notching devices of the type in question, the incision roller is power driven, and positioned substantially at a tangent to the surface of a pressure roller that turns idle on a second shaft, disposed substantially parallel to the shaft of the incision roller, and is capable of shifting transversely in relation thereto through the agency of a preloading device, this normally embodied as a calibrated spring associated with the second shaft. The function of the preloading device is to control the force with which the cutting edge of the blade, or blades, is brought into contact with the surface of the pressure roller as the incision roller turns.
In operation of the notching device, a continuous strip of transparent outer wrapping material with a previously incorporated, axially disposed tear-open ribbon, is fed between the incision and pressure rollers at right angles to the relative shafts in such a way that cuts are made at regular intervals along the line of the ribbon by interaction of the single blade or blades of the incision roller with the surface of the pressure roller.
Practical experience with notching devices of the type thus described has revealed that finished cuts seldom reflect the exact same U shape as that of the blade, i.e., are seldom effected faultlessly through both the strip and the ribbon, due to less-than-perfect parallelism between the two shafts that carry the incision and pressure rollers, attributable to fit tolerances allowed in assembly, and to uneven wear on the blades. Indeed it will often happen that the finished cut exhibits one part corresponding to the curve of the letter `U`, and a further part that corresponds to one only of the straight side members of the blade.
When, at a later stage, the continuous strip is cut transversely into discrete lengths each of which will be folded to form the transparent outer wrapper of a relative pack, the sub-standard nature of the transverse cuts aforementioned gives rise to marked difficulties experienced by the consumer in lifting the severed tab of the tear-open ribbon clear of the pack, and consequently, in effecting removal of the transparent outer wrapper.
Accordingly, the object of the present invention is to embody a notching device that will be capable of overcoming this drawback. A further object of the invention is to embody a notching device that can be adjusted at any given moment, simply and readily, and without halting the production cycle, so as to obtain notches of a shape that corresponds faultlessly to the profile of the relative blade or blades.